The present invention is directed to a method for designing a gasket for fluid sealing for severe acid environments, e.g. in alkalization plants.
Sealing gaskets have been used in a variety of different applications. The construction of such gaskets is typically the function of the application, the environment in which the gasket will be utilized, the stress load and other factors. Where gaskets are intended to be used in severely corrosive environments, the gasket construction will preferably also take into account the location of the seal(s), the need for a plurality of seals to isolate the primary seal from the corrosive environment, and the need to seal the imperfections on opposing surfaces of the pipe flanges, caused by erosion from the corrosive material following through the pipe. Such imperfections are most common near the inner radius of the pipe flanges, which is closest to the corrosive material flowing through the pipe. Consequently, it is preferable to locate the primary sealing element away from the inner radius of the gasket, where the adjacent surface of the flanges is less likely to bear such imperfections.
The particular gasket material is also a factor that is affected by application and environment factors. A softer, more readily conformable material can be useful to seal imperfections in the flange surfaces near the flange inner radius. However, such softer material may be less suitable to provide a proper seal (of sufficient stress load) to isolate the primary seal from the corrosive material flowing through the pipe.
Further, many sealing elements operate most effectively at relatively high stress levels, e.g. 20,000 to 30,000 psi or more. However, the greater the load bearing surface of the gasket, the more distributed the gasket stress, and the lower the stress per square inch.
Accordingly, to achieve the optimum gasket design, consideration must be given to not only the general gasket architecture, bolt load, desired gasket stress, and environmental factors, but must also consider the need for the different gasket components to function cooperatively in a specific application. As such, the size, material, and functional characteristics of the individual gasket elements must be carefully engineered for cooperative interaction. Because different portions of a multi-element gasket may have different load bearing stress characteristics, sealing characteristics and compressibility, the gasket design is preferably optimized for a load specific application, allowing each element to contribute to the functionality of the gasket, without degrading the contribution of other elements.
The present invention is directed gasket design process, and a multi-zone gasket architecture, wherein each zone optimized for a specific function by a design process that produces a gasket that, under a normal load, can produce a consistent gasket sealing stress of 20,000 psi or more on the primary sealing element, which is effectively sealed from the corrosive environment, while also being sufficiently soft to seal imperfection in the flange surfaces.
These and other features, objects and advantages of the invention are described below, in conjunction with the illustrated embodiments.